1. Field of the Invention
The present invention relates to a sliding bearing which is operated for a sliding motion on a flat or curved surface or along a shaft and is used in office equipment, acoustic or audio apparatus, measuring instruments, and the like.
2. Description of the Prior Art
Formerly, linear-motion sliding bearings combined with a track have been used as the sliding guide mechanism for linearly sliding parts of various devices. These sliding bearings has a sliding surface which faces the flat sliding surface of the track and moved linearly back-and-forth along the track. Lubrication oil (liquid lubricant) or grease (semi-solid lubricant) is applied to the sliding surface of the track beforehand to reduce friction and wear of the sliding surface of the linear-motion sliding bearing and the sliding surface of the track. Also, A small depression is formed on a portion of the linear-motion sliding bearing in which the lubrication oil or grease is stored, and from here it is supplied to both sliding surfaces.
However, when lubrication oil or grease is applied beforehand to the sliding surface of the track, if the amount applied is too little, the lubricant runs out in a short time. On the other hand, if the amount applied is too much, lubricant is scattered and splashed when the linear-motion sliding bearing moves over the sliding surface of the track. Not only is this a waste of lubricant, but the lubricant that is scattered and splashed dirties the equipment that is near the linear-motion sliding bearing.
In the case of grease, because it is a semi-solid lubricant, the amount of scattering or splashing is inclined to be less than for lubricating oil, but it is limited in a reduction of the friction characteristics, and the ability for the lubricant to be drawn and spread over the sliding surface is poor, therefore improvement of the wear characteristics is worse than that of lubricating oil.
Also, even when the lubricating oil or grease is stored in a shallow depression formed on part of the linear-motion sliding bearing, as the sliding speed of the linear-motion sliding bearing increases, the lubricating oil or grease is scattered or splashed, and the same problems as mentioned above of the lubricant running out in a short time, or the lubricant being splashed and dirtying the surrounding equipment are still unsolved.
Meanwhile, there is a conventional sleeve-type sliding bearing which engages and slides along a shaft, for example, as a mechanism for guiding the sliding motion of parts which make up an apparatus. The inner peripheral sliding surface of this bearing opposes the external sliding surface of the shaft.
A synthetic resin with good self-lubricating characteristics is used independently for such a conventional sliding bearing. To improve the friction- and wear-resistance of the synthetic resin material, for example, a synthetic resin is impregnated with several percent by weight of lubricating oil, or the like, and a solid lubricating agent or lubricating oil, or a wear-resistant fiber such as carbon fiber or the like, are used independently or in combination dispersed throughout the synthetic resin.
However, whether the synthetic resin is used independently or used with a lubricating agent or fiber material dispersed throughout, satisfactory friction- and wear-resistance has not as yet been obtained for the sliding surface. For this reason it is often necessary to apply to the sliding surface of the bearing a lubricating agent such as lubricating oil or grease.
In such a case however, when the amount of application is small, the friction factor is sufficiently low at the beginning of the bearing operation, but the lubricating agent runs out after the bearing has been in use for only a short time. Therefore there is the problem that the friction- and wear-characteristics of the bearing deteriorate conspicuously.
In addition, when the amount of application of the lubricant is excessive, a phenomenon of lubricant outflow occurs or the lubricating agent is expelled when the bearing slides, causing the problem of soiling around the periphery of the bearing.